Vehicle underfloor structure

ABSTRACT

A vehicle underfloor structure includes a battery having at least one connector projecting from a front end of the battery, and a protector covering and protecting the at least one connector from below, the protector having a rear portion attached to the battery and a front portion fastened to an attachment bar by a fastening bolt. The protector includes a fastening hole through which the fastening bolt is inserted, and a cutout connected to a rear portion of the fastening hole and allowing the fastening bolt to separate from the protector.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of co-pending U.S. patentapplication Ser. No. 16/548,092 filed on Aug. 22, 2019, which claimspriority to Japanese Patent Application No. 2018-157711 filed on Aug.24, 2018, both of which are incorporated herein by reference in theirentirety including the specification, claims, drawings, and abstract.

TECHNICAL FIELD

Disclosed herein is a vehicle underfloor structure in which a battery isdisposed under a floor of a vehicle.

BACKGROUND

A vehicle having a battery disposed under a floor of the vehicle hasbeen widely known hitherto. For example, JP 2017-109597 A discloses atechnique for disposing a battery under a floor of a vehicle. Accordingto JP 2017-109597 A, a connection member (connector) between the batteryand refrigerant piping is provided at a front end of the battery.According to JP 2017-109597 A, a protector that is a curved plate isdisposed extending downward from a front of the connector and preventsthe connector from coming into contact with an object dropped on a road(hereinafter referred to as an “on-road dropped object”).

In JP 2017-109597 A, the component to which the proximal end of theprotector is connected not specified, but it is presumed that theproximal end of the protector is connected to a body or frame(hereinafter referred to as “body or the like”). Such a body or the liketends to move rearward of a vehicle under a collision load in a frontcollision where a front of the vehicle collides with any obstacle. Inthe front collision, the protector connected to the body or the likealso moves rearward of the vehicle together with the body or the like.The technique disclosed in JP 2017-109597 A may cause the protector thathas moved rearward due to the front collision to collide with theconnector or the battery, thereby deteriorating or damaging theconnector or the battery.

Therefore, disclosed herein is a vehicle underfloor structure that canproperly protect the connector and the battery even in the frontcollision.

SUMMARY

A vehicle underfloor structure disclosed herein includes a batterydisposed under a floor of a vehicle and having at least one connectorprojecting from a front end of the battery, and a protector covering andprotecting the at least one connector from below, the protector having arear portion attached to the battery and a front portion fastened to abody or a frame by a fastening member. The protector includes afastening hole through which the fastening member is inserted, and acutout connected to a rear portion of the fastening hole and allowingthe fastening member to separate from the protector.

This configuration causes, in a front collision, the fastening membertogether with the body or the frame to move rearward of the vehicle toseparate from the protector. This disconnects the body or the frame fromthe protector to prevent the protector from colliding with the batteryor the connector, thereby properly protecting the battery and theconnector.

In this configuration, the protector may further include a rear slopesurface provided adjacent to a vehicle rear side of the fastening holeand inclined to ascend rearward.

This configuration causes the fastening member that moves rearward ofthe vehicle in the front collision to easily collide with the rear slopesurface inclined to ascend rearward. Then, when the fastening membercollides with the rear slope surface, the protector easily movesdownward, which makes a collision load less prone to being transmittedto the battery through the protector.

The protector may further include a plurality of raised parts and aplurality of recessed parts, the plurality of raised parts being raisedin a thickness direction and extending in a vehicle longitudinaldirection, the plurality of recessed parts being recessed in thethickness direction and extending in the vehicle longitudinal direction.

This configuration makes the protector less prone to being deformed inthe vehicle longitudinal direction. Accordingly, even in the frontcollision, the protector can easily separate from the body or the framewithout being deformed.

In this configuration, the fastening hole and the cutout are provided ineach of the raised parts, and a lower end surface of the fasteningmember is located higher than each of the recessed parts at positionsidentical to each other in the vehicle longitudinal direction.

This configuration causes both sides in a vehicle width direction of thefastening member to be surrounded by upright walls extending from theraised parts to the recessed parts. As a result, other members are lesslikely to collide with the fastening member, which in turn effectivelyprevents deterioration or loosening of the fastening member.

The at least one connector may be located above the recessed parts.

This configuration makes it possible to secure a distance between theconnector and the protector and effectively prevent the connector andthe protector from coming into contact with each other. As a result, theconnector can be protected properly.

The vehicle underfloor structure disclosed herein can properly protectthe connector and the battery even in the front collision.

BRIEF DESCRIPTION OF DRAWINGS

Embodiment(s) of the present disclosure will be described by referenceto the following figures, wherein:

FIG. 1 is a plan view of a section around a battery;

FIG. 2 is a view seen from A of FIG. 1;

FIG. 3 is a perspective view of a protector;

FIG. 4 is an enlarged view of a D section of FIG. 3;

FIG. 5 is a cross-sectional view taken along B-B of FIG. 1;

FIG. 6 is a cross-sectional view taken along C-C of FIG. 1;

FIG. 7 is a partial perspective view of an attachment bar as seen frombelow;

FIG. 8 is a schematic side view of a section around the battery and arear cross part without the protector or the attachment bar;

FIG. 9 is a schematic side view of the section around the battery andthe rear cross part with the protector but without the attachment bar;

FIG. 10 is a schematic side view of the section around the battery andthe rear cross part with the protector and the attachment bar;

FIG. 11 is a schematic cross-sectional view of a section around afastening hole in a normal state; and

FIG. 12 is a schematic cross-sectional view of the section around thefastening hole in a front collision.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the vehicle underfloor structure will be described withreference to the drawings. FIG. 1 is a plan view of a section around abattery 10. Further, FIG. 2 is a view seen from A of FIG. 1. Note that,in each of the drawings, “Fr,” “Up,” and “W” denote a vehicle frontdirection, a vehicle upper direction, and a vehicle width direction,respectively.

The vehicle V is an electric vehicle equipped with at least a motor as apower source, and is, for example, an electric vehicle that travels onlyby power from the motor, or a hybrid vehicle that travels by power fromboth the motor and an engine. Under a floor F of the vehicle V, thebattery 10 that transfers electric power to and from a traveling motoris disposed. The battery 10 is a chargeable and dischargeable secondarybattery such as a lithium ion battery. The battery 10 has a battery case17 made of metal. Inside the battery case 17, a battery moduleconstituted by a plurality of battery elements (cells) connected inseries or in parallel is housed. In this example, the battery case 17has a substantially rectangular parallelepiped shape that is flat, andelongated in a vehicle longitudinal direction.

A connector 18 that connects the battery module and an external deviceis attached to a front surface of the battery case 17. For example, asignal line, a power line, and a refrigerant pipe are connected to theconnector 18. The number of connectors 18 may be appropriately changedas needed, and may be one, or two or more. In the drawings, an examplein which three connectors 18 are provided on the front surface of onebattery case 17 is illustrated.

A suspension member 12 is provided adjacent to a vehicle front side ofthe battery 10. The suspension member 12 is a frame member that supportsa suspension. The suspension member 12 of this example includes a frontcross part 20 and a rear cross part 22 that extend in the vehicle widthdirection, and a pair of side parts 24 that each connect an end of thefront cross part 20 and an end of the rear cross part 22, and has asubstantially square shape.

As is apparent from FIG. 2, the front cross part 20 has an inverted archshape whose center in the vehicle width direction is concave. Further,the rear cross part 22 has an arch shape whose center in the vehiclewidth direction is convex. A lower end of the suspension member 12 islocated higher than a lower end of the battery 10. Further, lower endsof some of the connectors 18 are located lower than the lower end of therear cross part 22 at positions identical to each other in the vehiclewidth direction.

A protector 14 is laid between the suspension member 12 and the battery10. FIG. 3 is a perspective view of the protector 14, and FIG. 4 is anenlarged view of a D section of FIG. 3. Note that, in FIG. 4, in orderto make a through-hole identifiable, sandy hatching is applied to theprotector 14.

The protector 14 covers the connectors 18 from below to protect theconnectors 18 from contact with a road surface or a flipped stone. Theprotector 14 is a plate member long in the vehicle longitudinaldirection and is, for example, a press-molded member. The protector 14has a plurality of raised parts 28 that are raised in a thicknessdirection and a plurality of recessed parts 26 that are recessed in thethickness direction. The raised parts 28 and the recessed parts 26 eachextend in the vehicle longitudinal direction. Further, the raised parts28 and the recessed parts 26 are alternately arranged. As is apparentfrom FIG. 3, neither a width of each of the raised parts 28 nor a widthof each of the recessed parts 26 is constant, and the width of theraised part 28 is slightly decreased toward a vehicle rear side.Further, the width of the recessed part 26 is significantly increasedtoward the vehicle rear side.

A front portion of the protector 14 is fastened to the rear cross part22 of the suspension member 12 using an attachment bar 16 (to bedescribed later). For this fastening, at around a front end of theprotector 14, a fastening hole 30 is formed through which a fasteningbolt 42 that is a fastening member is inserted. A diameter of thefastening hole 30 is larger than a major diameter of the fastening bolt42 and smaller than a diameter of a head of the fastening bolt 42. Thefastening bolt 42 inserted through the fastening hole 30 is screwed intoa weld nut 43 fixed to the attachment bar 16 to fasten the protector 14to the attachment bar 16. FIG. 5 is a cross-sectional view taken alongB-B of FIG. 1, showing how this fastening is carried out.

The protector 14 further includes a cutout 32 that is located adjacentto a rear side of the fastening hole 30 and partially connected to thefastening hole 30 (see FIG. 4). The cutout 32 is sufficiently wider thanthe diameter of the head of the fastening bolt 42. The cutout 32 thusprovided allows the protector 14 and the attachment bar 16; that is, theprotector 14 and the suspension member 12, to easily disconnect fromeach other in a front collision. This will be described later.

Here, as shown in FIG. 4, a portion where the cutout 32 is formed isrecessed in a substantially V-shape. That is, the protector 14 includesa recess 34 constituted by a front slope surface 36 inclined to descendrearward and a rear slope surface 38 inclined to ascend rearward thatare connected to each other in the vehicle longitudinal direction. Aportion of the cutout 32 extends across the front slope surface 36. Therear slope surface 38 is a flat surface having neither a cutout nor ahole. It can be said that a rear end (i.e., an upper end) of the rearslope surface 38 is located higher than a lower end of the fasteningbolt 42 as described in detail later, and the rear slope surface 38faces the head of the fastening bolt 42 in the vehicle longitudinaldirection.

Further, as is apparent from FIGS. 3 and 5, the fastening hole 30, thecutout 32, and the recess 34 are all formed in each of the raised parts28. As shown in FIG. 5, a projection amount of the raised parts 28 fromthe recessed parts 26 is greater than a thickness of the head of thefastening bolt 42. In other words, a lower end of each of the recessedparts 26 is located lower than the lower end of the fastening bolt 42 ata position identical to the fastening bolt 42 in the longitudinaldirection. Accordingly, both sides in the vehicle width direction of thefastening bolt 42 are always surrounded by upright walls 40 extendingfrom the raised parts 28 to the recessed parts 26. This makes othermembers less prone to coming into contact with the fastening bolt 42,which in turn makes it possible to effectively prevent the fasteningbolt 42 from being damaged or loosened.

A rear portion of the protector 14 is attached directly to a bottomsurface of the battery 10 or indirectly to the bottom surface of thebattery 10 with a battery frame (not shown) or the like interposedtherebetween. The protector 14 may be attached to the battery 10 byfastening using a bolt or a rivet, or by welding. In any case, attachingthe rear portion of the protector 14 to the bottom surface of thebattery 10 allows the protector 14 to cover the connectors 18 projectingfrom the front surface of the battery 10 from below. This makes itpossible to protect the connectors 18 from contact with a road surfaceor a flipped stone.

In the meantime, in this example, such connectors 18 are disposed abovethe recessed parts 26 of the protector 14. This will be described withreference to FIG. 6. FIG. 6 is a schematic cross-sectional view takenalong a line C-C of FIG. 1. As is apparent from FIG. 6, the connectors18 are all located above the recessed parts 26. This configuration makesit possible to sufficiently secure a distance between each of theconnectors 18 and the protector 14 and accordingly prevent theconnectors 18 and the protector 14 from coming into contact with eachother. Further, such a configuration allows the protector 14 to bedisposed higher than a configuration where the connectors 18 aredisposed above the raised parts 28. As a result, the contact between theprotector 14 and the road surface can also be reduced.

As described above, the protector 14 is fastened to the attachment bar16. The attachment bar 16 is a member attached to a lower portion of therear cross part 22. FIG. 7 is a partial perspective view of theattachment bar 16 as viewed from below. In this example, the attachmentbar 16 is a rectangular tubular member elongated in the vehicle widthdirection. A through hole 44 used for fastening the attachment bar 16 tothe protector 14 is formed through a bottom surface of the attachmentbar 16. Further, onto a back surface side of the through hole 44, theweld nut 43 (see FIG. 5) into which the fastening bolt 42 is screwed isfixed.

A through hole 46 used for fastening the attachment bar 16 to the rearcross part 22 is formed at an end and through an upper surface of theattachment bar 16. Further, as shown in FIG. 7, the bottom surface ofthe attachment bar 16 that faces the through hole 46 is largely cut out,allowing insertion of the fastening bolt 48 from below. At a portion ofthe rear cross part 22 corresponding to the through hole 46, aninsertion hole through which the fastening bolt 48 is inserted isformed, and further, on a back surface side of the insertion hole, aweld nut 50 into which the fastening bolt 48 is screwed is fixed.However, the attachment of the attachment bar 16 to the rear cross part22 described here is an example, and the attachment bar 16 and the rearcross part 22 may be attached to each other by a different method suchas welding.

Here, as described above and shown in FIG. 5, the rear cross part 22 hasan arch shape whose center in the vehicle width direction is convex. Theattachment bar 16 is attached to a bottom surface of the rear cross part22 so as to extend across the arch. This produces a certain gap betweenthe upper surface of the attachment bar 16 and the bottom surface of therear cross part 22 at the center in the vehicle width direction.

As shown in FIG. 2, the attachment bar 16 may have a position and sizesuch that a lower end of the attachment bar 16 is located lower than thelower ends of the connectors 18 and higher than the lower end of thebattery 10. This configuration makes it possible to effectively preventthe protector 14 from coming into contact with an object dropped on aroad (hereinafter referred to as an “on-road dropped object”). This willbe described later.

Next, the reason why the protector 14 and the attachment bar 16 asdescribed above are provided will be described. FIGS. 8 to 10 areschematic side views of a section around the battery 10 and the rearcross part 22. FIG. 8 shows a configuration where neither the protector14 nor the attachment bar 16 is provided, FIG. 9 shows a configurationwhere only the protector 14 is provided but the attachment bar 16 is notprovided, and FIG. 10 shows a configuration where both the protector 14and the attachment bar 16 are provided.

Various objects (on-road dropped objects 100) are dropped on a road, andsome of the on-road dropped objects 100 are relatively large. When thelower end of the rear cross part 22 is located higher than the lowerends of the connectors 18, some of such on-road dropped objects 100 maycollide with the connectors 18. For example, as shown in FIG. 8, it isassumed that the on-road dropped object 100 is lower than the lower endof the rear cross part 22 but higher than the lower ends of theconnectors 18. In this case, the on-road dropped object 100 passes underthe rear cross part 22 and collides with the connectors 18 as thevehicle V travels, which may damage or deteriorate the connectors 18.

On the other hand, as shown in FIG. 9, it is assumed that the protector14 that covers and protects the connectors 18 from below is laid betweenthe rear cross part 22 and the battery 10. In this case, as in FIG. 8,even when the on-road dropped object 100 is present, the on-road droppedobject 100 collides with the protector 14 before colliding with theconnectors 18. Then, the collision of the on-road dropped object 100with the protector 14 causes the vehicle V to move upward to run overthe on-road dropped object 100, thereby preventing the connectors 18from colliding with the on-road dropped object 100.

However, since the protector 14 is a thin plate, the protector 14 may bedeformed or damaged when colliding with the on-road dropped object 100with a strong force. In this example, as described above and shown inFIG. 10, the attachment bar 16 is interposed between the protector 14and the rear cross part 22. The attachment bar 16 extends across thearch formed by the rear cross part 22. In other words, the attachmentbar 16 is attached to a position sufficiently lower than the center inthe vehicle width direction of the rear cross part 22. Accordingly, manyof the on-road dropped objects 100 collide with the attachment bar 16before colliding with the protector 14 as the vehicle V travels. Whenthe on-road dropped object 100 collides with the attachment bar 16, thevehicle moves upward to run over the on-road dropped object 100. As aresult, the contact between the on-road dropped object 100 and theprotector 14 is suppressed, which in turn effectively preventsdeformation or damage of the protector 14.

In general, the larger an angle between a direction of the force appliedto the protector 14 and the surface of the protector 14, the more theprotector 14 is prone to being deformed, and the more the direction ofthe force becomes parallel to the surface of the protector 14, the lessthe protector 14 is prone to being deformed. When the attachment bar 16is interposed between the protector 14 and the rear cross part 22, theheight of the front end of the protector 14 is lowered, and theinclination of the protector 14 becomes gentle. That is, an attachmentposture of the protector 14 becomes almost level. Accordingly, even whenthe on-road dropped object 100 collides with the protector 14, the anglebetween the direction (angle) of the force applied at the collision(generally, parallel to the road surface) and the protector 14 is small.As a result, even when the on-road dropped object 100 collides with theprotector 14, the protector 14 is less prone to being deformed.

Here, in order for the on-road dropped object 100 to pass under thelower end of the attachment bar 16 to avoid colliding with the protector14 and the connectors 18, the lower end of the attachment bar 16 may belowered to some degree. However, when the lower end of the attachmentbar 16 is excessively lowered, contact between the attachment bar 16 andthe road surface frequently occurs. Therefore, in this example, theattachment bar 16 has a position and size such that the lower end of theattachment bar 16 is located lower than the lower ends of the connectors18 and higher than the lower end of the battery 10. Such a position andsize makes it possible to prevent the on-road dropped object 100 fromcoming into contact with the protector 14 while suppressing contactbetween the attachment bar 16 and the road surface.

In the meantime, in the front collision where an obstacle collides withthe front of the vehicle V, a large force (collision load) directedrearward of the vehicle V is produced in the suspension member 12. Whenthe battery 10 and the suspension member 12 are connected by theprotector 14, the collision load is transmitted to the front portion ofthe battery 10. The rear portion of the battery 10 is rigidly fixed to abody or frame, so when such a collision load is transmitted to the frontportion of the battery 10, a compressive stress in the vehiclelongitudinal direction is undesirably produced in the battery 10.

Therefore, in this example, in order for the protector 14 and thesuspension member 12 to easily disconnect from each other in the frontcollision, the cutout 32 is provided adjacent to the rear side of thefastening hole 30 and connected to the fastening hole 30. Further, inthis example, as described above, the rear slope surface 38 inclined toascend rearward is further provided adjacent to the rear side of thefastening hole 30. An effect of the cutout 32 and the rear slope surface38 will be described with reference to FIGS. 11 and 12. FIGS. 11 and 12are schematic cross-sectional views of a section around the fasteninghole 30, wherein FIG. 11 shows a normal state, and FIG. 12 shows a statein the front collision.

Since the cutout 32 is connected to the rear side of the fastening hole30, as shown in FIG. 12, the fastening bolt 42 can easily move rearwardof the vehicle V. Accordingly, when the suspension member 12 and theattachment bar 16 fixed to the suspension member 12 move rearward in thefront collision, the fastening bolt 42 also moves rearward of thevehicle V and passes through the cutout 32. This causes the protector 14and the attachment bar 16; that is, the protector 14 and the suspensionmember 12 to disconnect from each other to prevent transmission of theload to the front portion of the battery 10.

Here, in this example, the rear slope surface 38 inclined to ascendrearward is provided adjacent to a rear side of the cutout 32. When thefastening bolt 42 passes through the cutout 32 and moves rearward, thehead of the fastening bolt 42 collides with the rear slope surface 38. Aforce produced by this collision is converted to a forward and downwardforce by the rear slope surface 38 inclined to ascend rearward to causethe protector 14 to easily move downward. Then, when the protector 14moves downward, load transmission to the battery 10 through theprotector 14 is more reliably prevented.

Note that, in order to cause the fastening bolt 42 to collide with therear slope surface 38, the upper end of the rear slope surface 38 needsto be located higher than the lower end of the fastening bolt 42.Generally, the steeper the inclination angle of the protector 14, thelower the location of the upper end of the rear slope surface 38. Inthis example, interposing the attachment bar 16 between the protector 14and the suspension member 12 makes the protector 14 almost level. Thus,a difference in height between the upper end of the rear slope surface38 and the fastening hole 30 can be suppressed, and the fastening bolt42 can be made to collide with the rear slope surface 38 more reliably.

Note that the above description is an example, and as long as at leastthe fastening hole 30 and the cutout 32 are formed in connection witheach other in the longitudinal direction at the front portion of theprotector 14, the remaining configuration may be changed as appropriate.For example, although in this example the protector 14 is fastened tothe suspension member 12 with the attachment bar 16 interposedtherebetween, the protector 14 may be fastened directly to thesuspension member 12 without the attachment bar 16. That is, a structureas shown in FIG. 9 may be employed. Further, the protector 14 may befastened to another frame or body rather than to the suspension member12.

Further, in this example, a bolt is used as the fastening member forfastening the protector 14 to the suspension member 12, but as long asboth the protector 14 and the suspension member 12 can be fastened toeach other, another fastening member such as a rivet or a clip may beused. Further, the shape of the protector 14 may be changed asappropriate, and may be, for example, a flat shape without any of therecessed part 26, the raised part 28, and the recess 34, or may becurved as a whole.

1. A vehicle underfloor structure comprising: a battery disposed under afloor of a vehicle and having at least one connector projecting from afront end of the battery; and a protector covering and protecting the atleast one connector from below, the protector having a rear portionattached to the battery and a front portion fastened to a frame by afastening member, wherein the protector includes a fastening holethrough which the fastening member is inserted, and a cutout formed witha rear portion of the fastening hole and allowing the fastening memberto separate from the protector.
 2. The vehicle underfloor structureaccording to claim 1, wherein the protector further includes a rearslope surface provided adjacent to a vehicle rear side of the fasteninghole and inclined to ascend rearward.
 3. The vehicle underfloorstructure according to claim 1, wherein the protector further includes aplurality of raised parts and a plurality of recessed parts, theplurality of raised parts being raised in a thickness direction of theprotector and extending in a vehicle longitudinal direction, theplurality of recessed parts being recessed in the thickness direction ofthe protector and extending in the vehicle longitudinal direction. 4.The vehicle underfloor structure according to claim 3, wherein thefastening hole and the cutout are provided in each of the raised parts,and a lower end surface of the fastening member is located higher thaneach of the recessed parts at positions identical to each other in thevehicle longitudinal direction.
 5. The vehicle underfloor structureaccording to claim 3, wherein the at least one connector is locatedabove the recessed parts.